A Palestinian suicide bomber blew himself up outside a trendy Tel Aviv nightclub on the Sabbath eve, as young people waited to get in. The attack rattled the two-week old cease-fire. Four Israelis were killed and about 50 wounded. Ambulances raced to the scene and quickly evacuated the wounded. The bomber came from the Tulkarem area in Samaria, where some militant groups oppose the truce. Israel demanded that the new Palestinian leader Mahmoud Abbas crackdown on terrorist groups, saying his efforts to negotiate with them have failed. Abbas responded that the Palestinian Authority would track down those responsible. Israeli and Palestinian security forces have arrested at least eight suspects in separate operations--a sign of rare security cooperation. The Palestinians say the Islamic terror group Hizbollah in Lebanon masterminded the attack.